NZ236947A

NZ236947A - Doctor blade for papermaking roll, made of plastics material

Info

Publication number: NZ236947A
Application number: NZ236947A
Authority: NZ
Inventors: Normand Boucher; Giancesare Bonetti
Original assignee: Albany Int Corp
Priority date: 1990-04-23
Filing date: 1991-01-30
Publication date: 1993-03-26
Also published as: NO911578L; DK73591D0; CA2039301A1; KR910018632A; AU7026591A; FI910481A; DK73591A; EP0454404A1; US5110415A; JPH04228695A; FI910481A0; NO911578D0; AU632661B2; BR9101133A

Description

<div class="application article clearfix" id="description"> Henry Hughes Ltd n\ •v. y Priority Date(s): Complete Specification F;lSP/.i/fti. Class: O^jG^Iqo; BU\ ffl/Q. 23 6 9 4 7 Publication Date: ...J993. P.O. Journal, No: ^dhk>. Patents Form 5 \ r^^STjOFrlCE. "60 i * **** " 11 —******* U~ N.Z. No. NEW ZEALAND Patents Act 1953 COMPLETE SPECIFICATION COMPOSITE DOCTOR BLADE AND A METHOD OF FASTENING THE SAME Q ON PULP OR PAPERMAKING MACHINE DOCTORS (/ ./ Cj& por<i.Wo/N Y*".. We, ALBANY INTERNATIONAL CORPORATION, A New York corporatin of 1373 thoH' Broadway, Albany, New York 12204, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement *>/ - 1 - (Followed by 1A) ? 3 6 9 4 7 BACKGROUND OF THE INVENTION a. Field of Invention This invention pertains to a blade used on a doctor for a pulp or papermaking machine, and more particularly to a blade made of a fiber reinforced composite material. Pulp or papermaking machines, utilize machine rolls. Such machine rolls are used during various aspects of the process, for example, in the forming, pressing, drying or calendering sections. The operation of machine rolls requires a device to remove contaminants which form on the roll surface and/or to peel off a sheet or web from the rolls. A traditional method of achieving this is through the use of a mechanical device commonly referred to as a doctor or doctor blade. The failure to remove the contaminants or the sheet effectively can have a catastrophic effect on the quality of the product being produced. The doctor blade is typically fastened to a structural beam which is adjustably supported across the papermaking machine on which a blade holder and a replaceable blade is provided. The doctor blade comes in direct contact with the roll surface so as to scrape off any contaminants from the roll surface inpl^diQg A* \ the whole pulp or paper web sheet or parts thereof. .. IA ? 3 6 9 b. Description of the Prior Art There is a plurality of different doctor blade types having dimensions and materials commonly available in the industry, as well as different designs of blade holders. Laminated plastic doctor blades and blade holders such as type KF-35, KF-35A or PNEUFLEX blade holder are manufactured by Albany International Corporation, the assignee of the present invention. For obvious reasons the blade should be securely attached to the blade holder as a doctor without a blade will not scrape anything from the roll, and as aforesaid, this will have a catastrophic effect on the machine production. But even worst, the blade or a part thereof can .come off and fall in the process where it will irreparably damage the pulp or paper machine clothing, and possibly the roll, because of direct and sudden contact with the blade holder. The ultimate solution to prevent the aforesaid catastrophic situation would be to permanently fasten the blade to the holder or to make it as an integral part of the holder. But, doctor blades do wear with time. Depending on the application, they can last anywhere from a few hours to several months. Therefore, a doctor blade must be a replaceable item. The blade and holder design should allow for easy, fast and safe blade replacement so as to insure that neither the blade or part thereof, like the fastening devices for example, will come off and fall into the process. 2 23694 A common .design in the industry is to put along one edge of the blade, some types of rivets, or some other mechanical fitted to the blade. The holder is then manufactured with a slot incorporating a step or a groove. The edge of the blade with the retainers can be slid into the groove through one end of the holder. Alternative designs are also available which allow a blade to be removed from the front of the holder, for the few applications where the access through the ends is limited. However, all these designs although widely used in the industry have a significant drawback as very often a retainer will come off the blade, and will either fall into the process, or will stay in the holder but become wedged into the blade slot, thus making the blade very difficult to slide in or out. Another design used in the industry consist of making the blade with built-in retainers whereby there is no mechanically fastened part on the blade that can come off. One known way to do this is to machine the blade out of thicker material, leaving a narrow step along one edge that will retain the blade in the holder slot. This method is widely used to manufacture polyethylene doctor blades, where machining is fast and easy, and where thicker material is also required to add strength or to increase wear life. Theoretically, this method can be used to manufacture blades out of other popular materials, like metal or laminated plastic. However, the extended cost of the material retainers that could be, for example, rivetted, glued, or press- and machining time combined with the high amount 3 ? 3 6 9 4 7 required, render this method simply undesirable. Moreover, it would not be suitable for the front removable blade design. Another known way of making built-in retainers to the doctor of the blade at a certain spacing, to simulate the function of the rivets of the first design. A typical drawing of the industry standard is shown in Figures 1 and 2. However, this design has been used only to manufacture metallic doctor blades, such as bronze or stainless steel for example. It was believed that the mechanical properties of synthetic material used in the doctor blade industry, those of laminated glass fiber reinforced plastic, for example, did not allow this method to be used on plastic blades. All the laminated composite doctor blades known to be used on the pulp or paper machines today, are manufactured with add-on retainers that are either rivetted, glued, or press-fitted along one edge of the blade, a design with major disadvantages as described above. One such prior art rivetted composite doctor blade is shown in Figure 3. OBJECTIVES AND SUMMARY OF THE INVENTION It is therefore a principle objective of the invention to provide a laminated plastic doctor blade with build-in retainers, thereby offering all the advantages relating to this design yet cost effective to manufacture. A blade is made in accordance with this invention by taking an elongated strip of reinforced composite material and ptiiSbfiirfgy I-\ blade is to stamp or punch pairs of short recesses along one edge 4 236947 a plurality-of, elongated recesses adjacent to a longitudinal side of the material. The recesses are formed by making cuts which are made long enough so that the plastic or permanent deformation of the material in the region around each recess is avoided. The cuts are made by a method which fibrillates the material along the plane of the cut so that irregularities are formed in the material along the cut which prevent the recessed material from returning to a normal position. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a plan view of a prior art metallic doctor blade discussed above; Figure 2 shows a partial side view of the prior art doctor blade of Figure 1; Figure 3 shows a side view of a rivetted plastic prior art doctor blade; Figure 4 shows a plan view of a plastic laminated doctor blade constructed in accordance with this invention; Figure 4A shows an enlarged partial plan view of the blade of Figure 4; Figure 4B shows an end view of the doctor blade of Figure 4; Figure 5 shows a partial side view of the doctor blade of Figures 4, 4A, 4B; Figure 6 shows a partial sectional view taken along line VI-VI in Figure 4; 5 936947 Figure 7 shows a doctor blade constructed in accordance with this invention inserted into a blade holder; Figure 8 shows a side view of the holder of Figure 7 being Figure 8A shows an alternate embodiment for the holder and blade of Figure 8; Figure 9 shows a front view of a punch-and-die assembly used to punch the recess in the blade of Figures 4-8; Figure 10 shows an end view of the punch-and-die assembly of Figure 9; Figure 11 shows a plan view of an alternate embodiment of the invention; Figure 12 shows a side view of the embodiment of Figure 11; Figure 13 shows a plan view of yet another alternate embodiment of the invention; Figure 14 shows a blade holder for the embodiment of Figure 13; and Figure 15 shows yet a further embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION Referring to Figures 1 and 2, one known doctor blade 10 consists of an elongated strip 12 made of stainless steel, bronze, or other alloys. One longitudinal side 14, strip 12 is beveled to form an edge. Along the opposite side, strip 12 is provided with a plurality of short punchings 16 punched into the member 12. Preferably, punchings 16 are formed in pairs as inserted into the holder; shown, and each punching is about 3/8" (9.5 mm) 6 P3694 punchings are made by permanently or plastically elongating and deforming the material of the strip to form the shown structure. This process could not be used on a reinforced composite blade because such materials are fragile and when they are punched they do not deform plastically, but rather they break quickly. Figure 3 shows another prior art doctor blade 18 made of a composite plastic material which at regular intervals is provided with a protruding rivet 19. A doctor blade 20 constructed in accordance with the present invention and shown in Figures 4, 4A, 4B, 5 and 6 consists of a strip 22 made of a fiber reinforced laminated plastic material such as a plastic laminated base of, for example, a vinyl esther reinforced by fiberglass fibers. In a preferred embodiment of the invention, strip 22 is about 0.060 (1.5 mm) thick, and 3" (78 mm) wide. One side 24 of strip 22 is bevelled at an angle of about 45' to form a sharp doctoring edge 25. Adjacent to the other side 26 of the strip 22, there are a plurality of recesses 3 0 extending along the length of the strip. At least one end of the strip 22 is provided with a through hole 32 by which the strip can be grabbed so that it can be removed from a holder. As shown in more detail in Figure 4A, each recess 30 is formed by making two parallel cuts 34, 36 in the strip 22. Because the strip is made of fiber glass reinforced composite material, as described above, the cuts 34, 3 6 are not perfectly planar, but are somewhat irregular with the inner surfaces of the cuts having a plurality of irregular fibrillations 38 (shotiif 7 256947 Figure 6). ^ (For the sake of clarity, in Figure 4A the irregularities of cuts 34 and 36 are shown somewhat exaggerated) . Preferably, simultaneously with the cutting, the strap 40 is corresponding recess.' The length and spacing of the cuts 34, 36 and their distance from side 26 are selected to insure that as substantially, elastically, whereby the strip 22 is not permanently deformed. In this manner, the strap 40 is not broken off but remains attached to the strip at both ends to form the recesses. The strap 40 is retained in the position shown in Figure 6 by the interference created between the fibrillations on the surfaces formed by cuts 34, 36. Typically, each strap 40 may be, for example, about 1" (25 mm) long and 3/16" (4mm) wide, and may be disposed at least 1/8" (3mm) away from edge 26. Referring now to Figures 7 and 8, a typical flexible doctor blade holder 50 consists of an elongated first member 52 secured to a frame (not shown). Several fingers 58 equally spaced along first member 52 as shown. Each finger 58 includes a-channel 66. After blade 20 is formed as described above with reference to Figures 4-6, it may be inserted into the holder by sliding it into cavity 62 in direction A, with recesses 30 sliding through channel 66. A sharp tool may be used to engage hole 32 to pull the blade into the holder. The holder is made to have dimensions just slightly larger than the blade whereby, once the blade is pushed out laterally with respect to the strip 22 to form the the recess is formed the material around the cuts is deformed 8 D C ? 3 6 9 "7 f r. f • seated in its place it is maintained there by interference fit with the holder. Additionally a hole 70 may be made at the ends of the holder. After the blade is inserted a pin is then introduced through hole 70, and hole 32 in the blade, thereby 5 securing the blade in place. In Figure 7 blade shown with edge 25 positioned for doctoring a roller 64. The fingers 58 are spaced at a preselected distance of, for instance, 2 inches. For the embodiment of Figure 8, in order to insure that at least some of the recesses 30 are captured between 10 the fingers 58 and member 52, they are spaced at odd intervals, i.e. an odd number of inches. In the preferred embodiment of Figure 8A, the blade 20 is not inserted longitudinally. Instead the blade 20 is first positioned so each recess 30 is disposed between two fingers 58 15 and the blade is advanced laterally between plate 52 and fingers 58. The blade is then moved longitudinally, as indicated by arrow B until the recesses 30 are captured within channels 66 of -fingers 58 and member 52. For this embodiment the recesses 30 must be spaced evenly with the spacing of the fingers 58. The 20 blade may now be secured as described above. This embodiment is used in environments where there is insufficient lateral space to slide the blade longitudinally into the holder. Figures 9 and 10 show a punch-and-die assembly 80 which may be used to make the recesses 30 in a strip 22. The assembly 80 25 includes a table 82 with two vertical uprights 84, 86. On table 82 there is a blade holder 88 for holding a blade 22. A lip o"' ii - « ,Jl/i A '^3 236947 on holder 88 helps position the strip 22. The holder also has an arcuate depression 92 positioned at a distance from lip 90 to define the position and dimensions of the recesses. Above the table 82 there is a member 94 movable vertically on the uprights 84, 86 as shown. This member 94 has a lower extension 96 disposed exactly above depression 92 and dimensioned to be complementary in size and shape to the depression. Thus, without the strip 22, when the member 94 lowered on the holder 88, extension 9 6 fits snugly into depression 92. The operation of assembly 80 is obvious from the above description. The strip 22 is first placed on holder 88 and then the member is forcefully lowered or dropped onto the strip 22. The shear formed at the interface between extension 96 and depression 92 generates the cuts 34, 36, and strap 40, and extension 96 pushes the strap 40 down to deform it elastically to form a recess. After each recess is made the strip is repositioned for the next recess by shifting it laterally. Alternatively the assembly 80 may be modified to make all the recesses simultaneously. Of course, other devices may be used to make the recesses as well. An alternate embodiment of the invention is shown in Figures 11 and 12. In these Figures, strip 100 is made with two sets of recesses 102, 104 the difference between the two sets being that while recesses 102 are punched from the bottom, recesses 104 are punched from the top of strip 100 as shown. In the embodiment of Figures 11 and 12 the recesses 102 10 236947 A further embodiment of the invention is shown in Figure 13 wherein strip 110 is also formed with two sets of recesses 112, 114. However in this latter embodiment recesses 112 are laterally offset from recesses 114. A holder 116 for a doctor blade made like strip 110 is shown in Figure 14. In this Figure, the holder 116 is made with a much wider channel 118 to accommodate both recesses 112, and 114 as shown* Finally, the recesses may be formed by means other than two parallel cuts. For example as shown in the embodiment of Figure 15, a blade 120 may be made with recesses 122 formed by a single curve, dimensioned and shaped to cut out sufficient material to allow elastic deformation. As previously described, the recess will hold in place because of the fibrillation of the material along the curved cut. Similarly, numerous other modifications may be made to the invention without departing from its scope as defined in the appended claims. 11 </div>

Claims

<div class="application article clearfix printTableText" id="claims"> ft {' 23C!^1 WHAT WE CLAIM IS: o 1. A doctor blade comprising: an elongated strip made of a plastic material, and having first and second sides and first and second surfaces extending between 5 said first and second sides, said material forming protrusions along cutting line when sheared; and a plurality of offset means formed on said strip' to extend the effective thickness of said blade, said offset means being formed of material which is maintained in place by said protrusions. 10 2. The doctor blade of claim 1 wherein said material is a plastic composite material. 3. The doctor blade _ of claim 1 wherein said strip has first and second opposed surfaces, and said offset means protrude above one of said surfaces. 15 4. The doctor'blade of claim 3 wherein said plurality offset means are partitioned into a first group of offsets and a second group of offsets , said first'group protruding above said first surface, and said second group of offsets protruding below said second surface. rj)0 5. The doctor blade of claim 4 wherein the offsets of said first group alternate with offsets' from said second group. 6. The doctor blade of claim 2 wherein each offset} means comprises a strap formed by a pair of parallel cuts in said strip, each cut defining interfacing surfaces, said interfacing surfaces having 25 protrusions which maintain said strap laterally offset from said strip. . ; / 12 nij , 2 7 MOV i'992 • .r,J 23 6947 7. The doctor blade of claim 6 wherein said strip is formed of a ■ "s reinforced composite material. 8. The doctor blade of claim 6 wherein said strip is made of a plastic material reinforced with fiberglass fibers. 5 9. The doctor blade of claim 8 wherein said plastic material is a laminated vinyl esther. 10. A doctor blade assembly comprising: a. doctor blade holder means consisting of an elongated member with a longitudinal cavity; 10 b. a doctor blade formed of an elongated strip made of a reinforced composite plastic material,, said blade having first and second opposed sides, said material forming protrusions along a cutting line when sheared, and a plurality of offsets formed near one of said sides to increase the effective thickness of said blade, said offsets being formed of material which is maintained in place by said protrusions, said blade being coupled to said holder means with said offsets being disposed inside the cavity, said cavity and said offsets cooperating to capture said blade. O 11. The doctor blade assembly of claim 10 wherein said offsets; consist of a strap of the same material as said strip. ...20 12. The doctor blade assembly of claim 10 wherein said strip has first and second opposed surfaces, and said offsets protrude above one of said surfaces. 13. The doctor blade assembly of claim 12 wherein said plurality offsets are partitioned into a first group of offsets 25 and a second group of :offsets , said first group protruding above ,/V 13 ° J A fit In °h f -l.-T C1.,.;'.'' said first surface, and said second group of offsets protruding below said second surface. 14. The doctor blade assembly of claim 13 wherein the offsets of said first group alternate with offsets from said second group. 15. The doctor blade assembly of claim 10 further comprising securing means for securing said blade to said holder means. 16. A method of securing a doctor blade made of a reinforced composite material, said material forming protrusions along a cutting line when sheared, to a blade holder, said blade holder including a longitudinal cavity, said method comprising the steps of: a. providing an elongated, generally rectangular strip of said reinforced plastic material having at least one longitudinal side; b. forming a plurality of offsets in said strip along said one side by making cuts in said strip, causing protrusions to form along said cutting line, and offsetting a section of material adjacent said cuts to increase the effective thickness of said strip, said offsets being maintained in place by said protrusions and said offset sections having a length selected to deform said sections elastically, to form a doctor blade; and c. inserting said doctor blade into said cavity, said cavity and said offset sections cooperating to hold said blade. 17. The method of claim 16 wherein each said section is formed between two interface surfaces with protrusions, said protrusions cooperating to maintain said sections in an offset position. 236947 19. The method of claim 16 wherein said holder includes a plurality of fingers and said cavity is formed by cavity longitudinal channels wherein said blade is inserted into said cavity transversely between said fingers. 20. The method of claim 16 wherein said blade is made of fiberglass reinforced plastic material. 21. A doctor blade substantially as herein described with reference to the accompanying drawings, figures 4 to 15. 22. A doctor blade assembly substantially as herein described with reference to the accompanying drawings, figures 4 to 15. 23. A method according to claim 16 substantially as herein described or exemplified. ALBANY INTERNATIONAL CORP By Their Attorneys HENRY HUGHES LIMITED Per- </div>